Stem cells are characterized by their multi-lineage differentiation potential (pluripotency) and their ability for self-renewal, which permits them to proliferate while avoiding lineage commitment and senescence. There has been much interest in identifying the pathways by which stem cells choose between the cell fates of lineage commitment versus self-renewal. A better understanding of this process would allow for the development of specific modulators that direct stem cell fate and improve their utility for regenerative therapies. Recent studies have demonstrated that mitochondrial function regulates gene expression and self-renewal in multiple cell types but little is known about the role of mitochondrial function in embryonic stem cells. We therefore studied the mitochondrial function and activity in human embryonic stem cells (hESCs). Our novel preliminary data suggest that when compared to differentiated cells, undifferentiated hESCs have high mitochondrial biogenesis, but exhibit low levels of mitochondrial glucose oxidation. Based on our data and recent published findings, we have formulated the central hypothesis of the proposal glucose oxidation regulates self-renewal and differentiation of human embryonic stem cells (hESCs). We propose to evaluate this by testing the following three hypotheses: In Aim 1, we will assess the effect of modulating glucose oxidation on the metabolic activity of hESCs. In Aim 2, we will evaluate the effect of modulating glucose oxidation on the self-renewal and differentiation of hESCs. In Aim 3, we will assess how enhancing mitochondrial glucose oxidation affects the therapeutic use of hESC by using in vivo models of teratoma formation and angiogenesis. This proposal investigates a new paradigm, since there is no clearly established link yet between mitochondrial glucose oxidation and human ESC fate. The results from our study of are likely to yield major insights into cellular metabolic and regenerative processes. Since multiple pharmacological modulators of metabolism are currently available and have been approved for use in patients, we believe that our findings on metabolic processes in stem biology could be readily translated into the clinical setting to improve regenerative stem cell therapies.